In recent years, from the viewpoint of energy conservation and miniaturization, light emitting devices (LED flashes) adopting light-emitting diodes (hereinafter, also called “LED”) as the light sources have been used as the light emitting devices for imaging cameras. As the light emitting devices described above, a light emitting device in which an LED and a Fresnel lens are combined is well known (see PTL 1, for example).
FIG. 1A is a sectional view of the light emitting device described in PTL 1. As illustrated in FIG. 1A, light emitting device 10 described in PTL 1 has substrate 20, light source substrate 21, light source 30 including a light emitting element and phosphors, and Fresnel lens 40. Fresnel lens 40 is disposed on substrate 20 to face a light emission surface of light source 30.
FIG. 1B is a sectional view of Fresnel lens 40. As illustrated in FIG. 1B, on one surface of Fresnel lens 40, refraction Fresnel lens section 41 and reflection Fresnel lens section 42 are formed. Refraction Fresnel lens section 41 and reflection Fresnel lens section 42 each have a plurality of tonic protrusions that are disposed in concentric circular shapes. Refraction Fresnel lens section 41 is formed in a position facing light source 30. Reflection Fresnel lens section 42 is formed around refraction Fresnel lens section 41 in such a manner as to surround light source 30. In Fresnel lens 40, a surface on which refraction Fresnel lens section 41 and reflection Fresnel lens section 42 are formed functions as incidence region 43, and a surface opposite to incidence region 43 functions as emission region 44.
In light emitting device 10 illustrated in FIG. 1A, light that is emitted from light source 30 at a small angle with respect to an optical axis is refracted in a predetermined direction in refraction Fresnel lens section 41, and is emitted from emission region 44. Light that is emitted from light source 30 at a large angle with respect to the optical axis is incident on incidence surface 45 of reflection Fresnel lens section 42, is reflected in a predetermined direction at reflection surface 46, and is emitted from emission region 44. In this manner, light emitting device 10 described in PTL 1 controls distribution of the light that is emitted from light source 30 by using Fresnel lens 40 that has refraction Fresnel lens section 41 and reflection Fresnel lens section 42.